Which is better--Parents in US or in China

I want to apply green card for my parents,I am not sure which way is better my parents stay in China or come US first.
I was told that it is faster if parents are in US.

Is it possible I submit I-130 while my parents are in China, once my petition get approval, is it possible for them to get visa to US and I file I485 in US, or my parents can't get visa since they have intention to immigrant?

Thank you very much!